add UDP network connection for physics client <-> server.
also set spinning friction in rolling friction demo (otherwise objects may keep on spinning forever)
add test for VR HUD/sub-titles
fix issue in previous commit, partial string use %.8s not %8.s
use long long int in b3Clock
fix warning/error in pointer alignment in serialization
Fix pybullet Windows compilation.
(thanks to bkeys/https://github.com/bulletphysics/bullet3/pull/687)